Blade holding apparatus

ABSTRACT

A doctor for supporting a flexible doctoring or wiping blade is disclosed as including a doctor back and blade holding apparatus comprising first, second, and third force-applying means for applying to the blade when the blade is in operative engagement with a work surface first, second, and third forces in alternately reversing directions along lines which are, respectively, parallel to and spaced increasing distances from the blade leading edge. The force applied by at least the third force-applying means is substantially proportional to the loading force applied by the work surface to the blade. The composite forces applied by the blade holding apparatus to the blade act to minimize the width-wise deflection of the blade and thus to maximize the length-wise flexibility thereof.

United States Patent 91 Dunlap 1 Jan. 23, 1973 BLADE HOLDING APPARATUS [75] Inventor: Harold E. Dunlap, Auburn, Mass.

[73] Assignee: Lodding Engineering Corporation,

Auburn, Mass.

22 Filed: April 7, 1970 21 Appl.No.: 27,201

[52] US. Cl ..l5/256.5l, 118/261 [51] Int. Cl ..D2lg 3/00,B31f l/14 [58] Field ofSearch ...1 18/203, 126, 261; 15/256.5l,

Primary Examiner-John P. McIntosh Attorney-Rosen & Steinhilper 57 ABSTRACT A doctor for supporting a flexible doctoring or wiping bladeis disclosed as including a doctor back and blade holding apparatus comprising first, second, and third force-applying means for applying to the blade when the blade is in operative engagement with a work surface first, second, and third forces in alternately reversing directions along lines which are, respectively, parallel to and spaced increasing distances from the blade leading edge. The force applied by at least the third force-applying means is substantially proportional to the loading force applied by the work surface to the blade. The composite forces applied by the blade holding apparatus to the blade act to minimize the width-wise deflection of the blade and thus to maximize the length-wise flexibility thereof.

7 Claims, 9 Drawing Figures PATENTEnJAnza 191a 3.711.888

sum 1 BF 3 FIG.2

INVENTOR HAROLD E. DUNLAP BY ROSEN 8: STEINHILPER ATTORNEYS BLADE HOLDING APPARATUS CROSS-REFERENCE TO RELATED APPLICATION This application related to application Ser. No. 793,950 filed Jan. 27, 1969 now U.S. Pat. No. 3,529,315, assigned to the assignee of the present invention.

BACKGROUND OF THE INVENTION A great variety of approaches have been taken to optimize the fit of a doctoring or wiping blade to the surface being doctored. One favored approach is to utilize a doctor blade which is as thin as possible and which therefore has, at least in its reststate, maximum length-wise flexibility. However, a thin blade held by conventional blade holding structures has a number of drawbacks. Because the blade has a low spring rate it deflects in a width-wise sense to a greater degree than would a less resilient blade. But this increased deflection augments the effective moment of inertia of the deflected blade cross section, and thus stifi'ens the blade along its length, decreasing its ability to conform to deviations in the doctored surface. Secondly, the exaggerated deflection produced by the high resiliency of the blade causes the blade angle, that is the angle which the blade makes with the work surface or a tangent thereto, to vary with blade loading.

Another shortcoming of present blade holders is their inability to seal the blade holder while in operation, with the result that the holder is very apt to clog with foreign matter, causing blade removal to be extremely difficult and possibly introducing false supporting surfaces.

OBJECTS OF THE INVENTION It is an object of this invention to provide doctor blade holding apparatus capable of supporting a blade so as to minimize the width-wise deflection of the blade and thus to maximize the length-wise flexibility thereof such that the blade is more able to conform to deviations in the doctored surface. It is thus an object to provide doctor blade holding apparatus capable of minimizing blade wear and variations in blade angle with blade loading, while optimizing the fit of the blade to the work surface.

It is another object to provide blade holding apparatus which establishes a relatively tight seal between the blade and the blade holding apparatus so as to minimize the entry of foreign matter into the blade holding apparatus.

It is yet another object of this invention to provide blade holding apparatus in the form of a cartridge which is capable of being easily and quickly inserted into and removed from a blade holder.

It is yet another object to provide blade holding apparatus which enhances the useful properties of the blade holding apparatus described and claimed in the above-noted copending application. More particularly, it is an object to provide blade holding apparatus enhancing the usefulness of a pliable fluid-filled closed tube as a means for causing a blade to conform to the profile of a work surface. Still more specifically, it is an object to provide blade holding apparatus effective to reduce the loading on such a tube to thus enable it to be used in heavy blade loading applications.

Further objects and advantages of the invention will in part be obvious and will in part become apparent as the following description proceeds. The features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of the invention, reference may be had to the following detailed description taken in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view, partly broken away, of blade holding apparatus embodying the teachings of this invention;

FIG. 2 is a side elevational view of a portion of the apparatus shown in FIG. 1;

FIGS. 3-5 are diagrams of forces operating on certain elements of the blade holding apparatus shown in FIGS. 1 and 2 in directions normal to the respective element;

FIG. 6 is a schematic and exaggerated representation of a working blade as it might appear in its deflected operative state; and

FIGS. 7-9 are end, side, and bottom views of a second embodiment of the invention showing elements of the novel blade holding apparatus assembled to form a cartridge.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The drawings depict a preferred implementation of the principles of this invention. In FIGS. 1-2 novel apparatus for doctoring or wiping a moving surface, here shown as a roll 10, is illustrated as comprising a working blade 12 held by blade holding apparatus 14. The blade holding apparatus is in turn supported upon a doctor back 16. The doctor back 16 is supported by a pair of trunnions, one of which is shown at 18. The trunnion 18 includes a shaft 20 which is bolted to the back 16 and mounted for rotation in a bearing 24. A loading device 26, which may be of any suitable type, is coupled to the shaft 20 through an articulated linkage 28 and is employed to place a predetermined loading of the blade 12 against the roll 10.

A blade holder is shown as comprising a top plate 30 secured to the doctor back 16 by means of bolts 32. A bottom plate 34 affixed to the top plate 30 cooperates with the top plate 30 to define an open-ended slot 36 which receives the blade 12 and other novel blade holding means, to be discussed in detail below.

As will be explained in detail below, blade holding apparatus according to this invention comprises first, second, and third force-applying means for respectively applying to the blade 12 first, second, and third forces in alternately reversing directions along lines which are, respectively, parallel to and spaced increasing distances from the blade leading edge 38.

In the illustrated embodiment, the means for applying the described first force on the blade 12 includes a rocker plate 40 having a forward edge 41 and a rearward portion 42. The forward edge 41 bears upon the blade 12, applying a force F along a line parallel to and spaced from the leading edge 38 of the blade 12.

Reference may be had in connection with the discussion to FIGS. 3-5 showing, respectively, diagrams of the forces acting substantially normal to the blade 12 per se, to the blade 12 and rocker plate 40 as an assembly, and to the rocker plate 40 alone. The force F is in opposition to the normal component F of the loading force applied by the work surface to the blade leading edge 38.

An oppositely directed reaction force F A is applied to the rocker plate 40 by a lip 45 on top plate 30. The rocker plate 40 acts as a first class lever pivoted about the lip 45 on top plate 30. The rocker plate 40 transmits a proportional part of the force F to separating means 46 to thus establish the described third force F along a line on the base portion 44 of the blade 12 parallel to the blade leading edge 38. In FIG. 5 which represents the force diagram on rocker plate 40, force F is a reaction force equal and opposite to force F,;

7 force F is a reaction force equal and opposite to force The described second force F is applied to the blade 12 by a lip 52 on bottom plate 34 which engages the blade 12 along a line between forces F and F F is oppositely directed from the forces F and F As shown in exaggerated dimensions in FIG. 6, the alternately reversing forces F F F and F in composite cause the working blade 12 to assume a gently curving S-shaped configuration having a relatively low width-wise deflection and moment of inertia about a neutral axis parallel to the length of the blade 12. Minimization of width-wise blade deflection by the force pattern created by this novel blade holding apparatus effects a maximization of the length-wise flexibility of the blade and thus of its ability to conform to or fit the surface being doctored.

The rocker plate 40, acting as a first class lever, functions to transmit a proportional part of the blade loading force to the separating means 46. Thus, the tendency of the width-wise deflection of the blade to increase with increasing blade loading is counteracted by the proportional increase in force F acting on the base portion 44 of the blade 12, the low moment of inertia configuration of the blade cross section being thereby maintained.

Further, minimization of the width-wise deflection of the working blade as a function of the blade loading reduces the variations in blade angle with changes in .blade loading.

The separating means 46 could be solid or could take any of a variety of forms but is here shown, by way of example, as consisting of a pliable but substantially inelastic tube (silicon or polyurethane, for example) charged with a suitable substantially incompressible fluid 48 such as glycerine or certain hydraulic fluids. The separating means 46, which operates on a volumetric displacement principle, is fully described and claimed in the above-referenced copending application and functions to conform the profile of the blade leading edge 38 to the doctored surface. Such a separating means 46 is capable of compensating for a crown on the roll, or for heat-inducted distortions or other deviations in the work surface.

As suggested above, blade holding apparatus constructed according to this invention enhances the usefulness of a filled tube separator as described for the reasons to follow. It is desirable that such a separator be relatively pliable in order to maximize its sensitivity to blade loading variations along the length of the blade. Thus the walls of the tube are preferably made as thin as possible. However, a thin-walled tube has definite loading limitations. By this invention, due to the nature of the rocker plate acting as a first class lever with a mechanical advantage of less than one, the tube experiences loading forces which are but a predetermined fraction of the blade loading forces. The magnitude of this fraction can be selectively varied by adjusting the width of the blade 12 or the effective lever arm lengths of the rocker plate 40. The lever arm lengths of the rocker plate 40 may be altered by varying the width of the rocker plate 40 and/or the location of the line along which the force F, is applied relative to the forward and rear edges of the rocker plate 40. By this invention, then, a highly sensitive deformable separating means, as described, can be used in heavyduty doctoring applications.

A buffer plate disposed between the separating means 46 and the blade 12 prevents damage to the separating means 46 when the blade 12 is removed for replacement, and facilitates removal thereof.

A base strip 54 slideably received in a selected one pair of a plurality of pairs of grooves 56 formed in the top and bottom plates 30, 34 determines the magnitude of the extension of the blade 12 and associated rocker plate 40 beyond the top plate 30. The use of an adjustable base strip 54 enables a worn blade to be reground and used again; the base strip 54 is moved forwardly with each reconditioning of the blade to successive groove pairs in order to maintain the blade extension constant.

A feature of this invention not yet discussed is the tight seal produced between the blade and the blade holding apparatus. This feature is especially useful in doctoring applications such as a top press doctor where quantities of contaminated fluids are present or where foreign matter such as clay, fuzz, dust, and the like are ever-present to form a cement-like substance which renders blade removal extremely difficult and which is apt to produce spurious support surfaces for the working blade. In novel blade holding apparatus following the teachings of this invention, when the blade 12 is placed in engagement with a work surface, the force F applied to the blade 12 by the rocker plate 40, the force F, applied by thelip 45 to the rocker plate 40, and the force F applied by the lip 52 to the working blade 12 each create a relatively tight seal impervious to entry of foreign fluid and solid contaminants.

FIGS. 7-9 illustrate another embodiment of the invention wherein the rocker plate, separating means, and base strip are packaged as a cartridge to facilitate insertion and removal of these elements as a unit from the slot 36 in the blade holder and to maintain their desired relative positions. FIGS. 7-9 show a working blade 60, a rocker plate 62, separating means 64, and a base strip 66, all performing the same functions as described above with respect to the FIGS. 1-2 embodiment. A buffer plate 68 has been modified to perform plural functions first, to protect the separating means 64, as described above, and second to provide means for retaining and positioning the separating means 64 between the rocker plate 62 and the working blade 60.

Referring particularly to FIG. 8, the buffer plate 68 is shown as having a number of bent-out tabs 70 which are spot welded to the rocker plate 62. The tabs 70 are deflected from the plane of the buffer plate 68 such as to cause the buffer plate 68 to extend in its unflexed state outwardly at a predetermined angle to the rocker plate 62. The restorative forces produced by the tabs 70 cause the buffer plate 68 to act as a leaf spring effective to capture and position the separating means 64 between the buffer plate 68 and rocker plate 62. The natural restorative forces in the tab 70 and the frictionalforces between the separating means and the plates 62, 68 effects secure retention of the separating means 64.

In order that the base strip 66 constitute part of the cartridge, the strip 66 is provided with a series of apertures 72 through which is passed a retainer 74. The retainer 74 has a plurality of tabs 76 which are spot welded to the rocker plate 62 so as to join in a loose connection the base strip 66 and the rocker plate 62. Thus, by this construction, all of the removable blade holding elements, namely the rocker plate 62, buffer plate 68, separating means 64, and base strip 66 are maintained in appropriate relative positions and are joined so as to be removable from or insertable into the blade holder as a unit.

The invention is not limited to the particular details of construction of the embodiments depicted, and it is contemplated that various and other modifications and applications will appear to those skilled in the art. For example, whereas the invention is illustrated as being incorporated in a Yankee creping doctor, the novel blade holding apparatus will also produce superior results when used to hold a wiping or coating blade, and is adaptable for use with other types of doctor backs, blades, and blade holders and in a great variety of doctoring applications. To alter the doctoring characteristics of the blade or for other reasons, the magnitude and characteristics of the described blade forces F F F and F can be' varied by appropriately changing the relative dimensions of the rocker blade, and other elements of the apparatus and by adjusting the inter-force distances.

Whereas the separating means has been illustrated in both of the described embodiments as comprising a closed, fluid-filled tube, the principles of this invention are equally valid and efficacious when a solid or other type of separator is used to space the tail portion of the rocker plate from the base of the working blade. Therefore, because certain changes may be made in the above-described apparatus without departing from the true spirit and scope of the invention herein involved, it is intended that the subject matter of the above depiction shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. For use with apparatus for doctoring or wiping a moving work surface which includes a flexible blade having a leading edge, blade holding apparatus for supporting the blade for engagement with the surface, comprising:

first, second and third force-applying means for respectively applying to the blade when the blade is in operative engagement with the surface, first, second and third forces in alternately reversing directions along lines which are, respectively, parallel to and spaced increasing distances from the blade leading edge, said force-applying means including rocker plate means pivoted about an axis running between the lines of application of said first and third forces for applying said first and third forces to said blade, and profiling means located between and effective to apply force to both said blade and said rocker plate for separating said blade from said rocker plate means'along the line of application of said third force, said profiling means including an elongated flexible member having the property that a given pressure applied to it in one location will appear substantially uniformly at other locations throughout its length for applying said third force substantially proportional to the normal component of the loading force applied by the surface on the blade, the composite forces applied by said holding apparatus to the blade acting to minimize the widthwise deflection of the blade and thus to maximize the length-wise flexibility thereof.

2. For use with apparatus for doctoring or wiping a moving work surface which includes a flexible working blade having a leading edge, blade holding apparatus for supporting the blade for engagement with the surface, comprising:

holder means defining a slot for receiving the blade;

a rocker plate received in said slot and having a forward edge engaging the blade along a line parallel to and spaced from the blade leading edge to establish a first force on the blade opposed to the force applied to the blade by the surface;

resilient separating means disposed between and in direct contact with both a rearward portion of said plate and a base portion of the blade providing a separation between them such that said plate makes an angle with the blade, said separating means including an elongated flexible profiling member having the property that a given pressure applied to it in one location will appear substantially uniformly at other locations throughout its length;

said holder means including first and second lips on opposite sides of said slot, said first lip engaging the blade along a line between said first force and said base portion of the blade to establish a second force opposed to said first force, said second lip engaging said rocker plate along a line between and parallel to said forward edge and said rearward portion thereof on the opposite side of said plate from the blade and nearer to said forward edge than said rearward portion, said rocker plate acting as a first class lever with a mechanical advantage less than unity pivoted about said second lip for transmitting a proportional part of the normal forces imparted by the blade on said rocker plate to said separating means and thus to establish a smaller third force along a line on said base portion of said blade which is opposed to said second force, the composite forces applied by said blade holding apparatus to the blade when in operation thereby acting to minimize the width-wise deflection of the blade and thus to maximize the lengthwise flexibility thereof.

3. The apparatus defined by claim 2 wherein said resilient separating means comprises an elongated pliable tube closed at both ends and containing a substantially incompressible fluid.

4. For use with apparatus for doctoring or wiping a moving work surface which includes a flexible working blade having a leading edge, blade holding apparatus for supporting the blade for engagement with the surface, comprising:

holder means defining a slot for receiving the blade;

a cartridge adapted to be insertable into and removable from said slot, comprising:

a rocker plate having a forward edge engaging the blade along a line parallel to and spaced from the blade leading edge to establish a first force on the blade opposed to the force applied to the blade by the surface,

separating means disposed between and spacing a rearward portion of said plate and a base portion of the blade providing a separation between them such that said plate makes an angle with the blade,

a resilient buffer plate having a forward portion and a tail portion, said forward portion being secured to said rocker plate along a line parallel to said forward edge of said plate such that said tail portion is free, said buffer plate receiving and retaining said separating means in direct contact between said tail portion thereof and said rocker plate; said blade overlying said buffer plate so that said blade may be installed in and removed from the holder without touching the separating means;

a base strip, and

means for securing said rocker plate to said base strip;

said holder means including first and second lips on opposite sides of said slot, said first lip engaging the blade along a line between said first force and said base portion of the blade to establish a second force opposed to said first force, said second lip engaging said rocker plate along a line parallel to and between said forward edge and said rearward portion thereof on the opposite side of said plate from said blade and nearer to said forward edge than to said rearward portion, said rocker plate acting as a first class lever with a mechanical advantage less than unity pivoted about said second lip for transmitting a proportional part of the forces imparted by the blade to said rocker plate to said separating means and thus to establish a smaller third force along a line on said base portion of said blade which is opposed to said second force, the composite forces applied by said blade holding apparatus to the blade when in Operation acting to minimize the width-wise deflection of the blade and thus to maximize the length-wise flexibility thereof.

5. The apparatus defined by claim 4 wherein said separating means comprises an elongated pliable tube closed. at both ends and containing a substantially incompressible fluid.

6. For use with apparatus for doctoring or wiping a moving work surface which includes a flexible working blade having a leading edge and a blade holder having a slot for receiving the blade, a blade holding cartridge comprising:

a rocker plate having a forward edge for engaging the blade along a line parallel to and spaced from the blade leading edge;

resilient separating means disposed between and spacing a rearward portion of said rocker plate and a base portion of the blade when installed such that said plate makes an angle with the blade installed in said holder;

a resilient buffer plate having a forward portion and a tail portion, said forward portion being secured to said rocker plate along a line parallel to said forward edge of said plate such that said tail portion is free, said buffer plate retentively receiving said separating means in direct contact between said tail portion thereof and said rocker plate; said blade when installed overlying said buffer plate, so that said blade may be installed in and removed from the holder without touching the separating means;

a base strip; and

means for securing said rocker plate to said base strip, whereby said rocker plate, buffer plate, separating means, base strip, and means for securing are insertable into and removable from said slot as a unit.

7. The apparatus defined by claim 6 wherein said separating means comprises an elongated pliable tube closed at both ends and containing a substantially incompressible fluid. 

1. For use with apparatus for doctoring or wiping a moving work surface which includes a flexible blade having a leading edge, blade holding apparatus for supporting the blade for engagement with the surface, comprising: first, second and third force-applying means for respectively applying to the blade when the blade is in operative engagement with the surface, first, second and third forces in alternately reversing directions along lines which are, respectively, parallel to and spaced increasing distances from the blade leading edge, said force-applying means including rocker plate means pivoted about an axis running between the lines of application of said first and third forces for applying said first and third forces to said blade, and profiling means located between and effective to apply force to both said blade and said rocker plate for separating said blade from said rocker plate means along the line of application of said third force, said profiling means including an elongated flexible member having the property that a given pressure applied to it in one location will appear substantially uniformly at other locations throughout its length for applying said third force substantially proportional to the normal component of the loading force applied by the surface on the blade, the composite forces applied by said holding apparatus to the blade acting to minimize the width-wise deflection of the blade and thus to maximize the length-wise flexibility thereof.
 2. For use with apparatus for doctoring or wiping a moving work surface which includes a flexible working blade having a leading edge, blade holding apparatus for supporting the blade for engagement with the surface, comprising: holder means defining a slot for receiving the blade; a rocker plate received in said slot and having a forward edge engaging the blade along a line parallel to and spaced from the blade leading edge to establish a first force on the blade opposed to the force applied to the blade by the surface; resilient separating means disposed between and in direct contact with both a rearward portion of said plate and a base portion of the blade providing a separation between them such that said plate makes an angle with the blade, said separating means including an elongated flexible profiling member having the property that a given pressure applied to it in one location will appear substantially uniformly at other locations throughout its length; said holder means including first and second lips on opposite sides of said slot, said first lip engaging the blade along a line between said first force and said base portion of the blade to establish a second force opposed to said first force, said second lip engaging said rocker plate along a line between and parallel to said forward edge and said rearward portion thereof on the opposite side of said plate from the blade and nearer to said forward edge than said rearward portion, said rocker plate acting as a first class lever with a mechanical advantage less than unity pivoted about said second lip for transmitting a proportional part of the normal forces imparted by the blade on said rocker plate to said separating means and thus to establish a smaller third force along a line on said base portion of said blade which is opposed to said second force, the composite forces applied by said blade holding apparatus to the blade when in operation thereby acting to minimize the width-wise deflection of the blade and thus to maximize the length-wise flexibility thereof.
 3. The apparatus defined by claim 2 wherein said resilient separating means comprises an elongated pliable tube closed at both ends and containing a substantially incompressible fluid.
 4. For use with apparatus for doctoring or wiping a moving work surface which includes a flexible working blade having a leading edge, blade holding apparatus for supporting the blade for engagement with the surface, comprising: holder means defining a slot for receiving the blade; a cartridge adapted to be insertable into and removable from said slot, comprising: a rocker plate having a forward edge engaging the blade along a line parallel to and spaced from the blade leading edge to establish a first force on the blade opposed to the force applied to the blade by the surface, separating means disposed between and spacing a rearward portion of said plate and a base portion of the blade providing a separation between them such that said plate makes an angle with the blade, a resilient buffer plate having a forward portion and a tail portion, said forward portion being secured to said rocker plate along a line parallel to said forward edge of said plate such that said tail portion is free, said buffer plate receiving and retaining said separating means in direct contact between said tail portion thereof and said rocker plate; said blade overlying said buffer plate so that said blade may be installed in and removed from the holder without touching the separating means; a base strip, and means for securing said rocker plate to said base strip; said holder means including first and second lips on opposite sides of said slot, said first lip engaging the blade along a line between said first force and said base portion of the blade to establish a second force opposed to said first force, said second lip engaging said rocker plate along a line parallel to and between said forward edge and said rearward portion thereof on the opposite side of said plate from said blade and nearer to said forward edge than to said rearward portion, said rocker plate acting as a first class lever with a mechanical advantage less than unity pivoted about said second lip for transmitting a proportional part of the forces imparted by the blade to said rocker plate to said separating means and thus to establish a smaller third force along a line on said base portion of said blade which is opposed to said second force, the composite forces applied by said blade holding apparatus to the blade when in operation acting to minimize the width-wise deflection of the blade and thus to maximize the length-wise flexibility thereof.
 5. The apparatus defined by claim 4 wherein said separating means comprises an elongated pliable tube closed at both ends and containing a substantially incompressible fluid.
 6. For use with apparatus for doctoring or wiping a moving work surface which includes a flexible working blade having a leading edge and a blade holder having a slot for receiving the blade, a blade holding cartridge comprising: a rocker plate having a forwarD edge for engaging the blade along a line parallel to and spaced from the blade leading edge; resilient separating means disposed between and spacing a rearward portion of said rocker plate and a base portion of the blade when installed such that said plate makes an angle with the blade installed in said holder; a resilient buffer plate having a forward portion and a tail portion, said forward portion being secured to said rocker plate along a line parallel to said forward edge of said plate such that said tail portion is free, said buffer plate retentively receiving said separating means in direct contact between said tail portion thereof and said rocker plate; said blade when installed overlying said buffer plate, so that said blade may be installed in and removed from the holder without touching the separating means; a base strip; and means for securing said rocker plate to said base strip, whereby said rocker plate, buffer plate, separating means, base strip, and means for securing are insertable into and removable from said slot as a unit.
 7. The apparatus defined by claim 6 wherein said separating means comprises an elongated pliable tube closed at both ends and containing a substantially incompressible fluid. 